The present invention concerns an improved process and certain intermediates useful for the synthesis of compounds of the formula ##STR1## where R is hydrogen or ##STR2## and R.sup.1 is a conventional hydroxy protecting group, particularly t-butyldimethylsilyl. These compounds are of known utility as intermediates in the synthesis of known valuable penem antibiotics and/or beta-lactamase inhibitors such as Sch 29482: ##STR3## See Ganguly et al., J. Antimicrob. Chemotherapy. 9, Supplement C, pp. 1-6 (1982).
The present intermediate compound wherein R is 1-(t-butyldimethylsilyloxy)ethyl is a known compound [Leanza et al., Tetrahedron 39, pp. 2505-2513 (1983)]. The present intermediates are converted to known, valuable penems (e.g. Ganguly et al., loc. cit., Hamanaka, European Patent Application 130,025; Daniels et al., J. Chem. Soc., Chem. Commun. 1982, pp. 1119-1120; Tanaka et al., ibid., pp. 713-714) according to known methods of alkylation (e.g. Leanza et al., loc. cit.), removal of allyl protecting groups (e.g., Ganguly et al., loc. cit.; Girijavallabhan et al., Tetrahedron Lett. 22, pp. 3485-3488 (1981), Jeffrey et al., J. Org. Chem. 47, pp. 587-590 (1982), and removal of silyl protecting groups [e.g., Hayashi et al., Chem. Pharm. Bull. 29, pp. 3158-3172 (1981)].